Arc-gap device



1929- T H. B. SMITH 1,731,875

ARC GAP nnvm's WITNESSES: INVENTOR 4 I Ham/0'5. 507w ATTORNEY Patented Get. 15, 1929 UNITED STATES PATENT QFFMIE HARGLD B. SMITH, OF VIQRCESTER, MASSACHUSETTS, AESIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, CORPQBATIUN QF PENNSYLVANIA ARC-GATE DEVICE Application filed September lily invention relates to arc-gap devices and p: ticularly to arc-gap voltage measuring terminals for high-voltage circuits.

One object of my invention is to provide simple and economical substitutes for spheregap terminals, and particularly for relatively large higlnvoltage terminals of spherical form which are expensive and diiiicult to construct to the required degree of accuracy.

Another object of my invention is to provide an arc-gap terminal device that may readily be provided for circuits of voltages of such relatively high values that the provision of the usual sphere-gap terminals therefor is impracticable, if not impossible.

It has been usual, in voltage-testing prac ties, to employ spaced conducting spheres or members having mini-spherical adjacent conducting surfaces.

To ensure accurate operation and consistent results, such devices must necessarily be of very accurate formation, a slight deviation from the true spherical iorm disturbing the electrostatic field and causing results which may or may not bear any regular mathematical relation to each other ifor different voltages and arcing distances.

l l ith the increase of commercial voltages, testing devices of this character become increasingly important and the provision of --suitable arcing terminals particularly for very high voltage measurements has already become a trouljilcsome problem.

It is my aim to overcome the dilliculties attending the provision and use of spheregap terminals for high-voltage circuits and to provide a device that shall not only be readily adaptable 1" r volts es of all values but that shall be crmremc y simple in con struction and economical to manufacture.

i rccordingly, in 1iiracticinp; my invention, 1 provide paired conducting terminals having portions oil such simple geometrical contour and other portions of such relatively small size as to render the same relatively easy to construct to the required degree of precision.

Figure l oi the accompanying drawings, is aside elevational view of a portion of voltage-measuring device embodying a pair s, 1925. Serial No. 55,193.

of arcing terminals constructed and related in accordance with my invention,

2 is a plan view of the members shown 1, and r l 3 is an enlarged detail side view, partially in section and partially in elevation, of one of the members shown in the other figures, illustrating one form of construction thereof.

The device comprises, in general, apair of terminal members embodying interme diate portions 1, end portions 2 and conducting; leads or supports 3 that are connected to the intermediate portions 1 and to a suitable framework or other supporting; struoture (not shown).

The in ermediate portions 1 are preferably of cylindrical form having true circular crosssectional area and being of relatively great length compared to the d.ia1netcrstliereoi". These portions, while preferably con structed of relatively thin sheet metal, such copper, may also be constructed and supported by insulating or other structural, or metallic material covered with metal foil or very thin metal or otherwise provided with conducting; surfaces.

The portions 1 are preferably disposed with the longitudinalaxes thereof in right-angular relation in spaced parallel planes, although they may be disposed in other relations and may be mounted for adj ustable relative movement in any suitable manner.

The portions 1 may further be of partially cylindrical, instead, of full cylindrical form, with the outer curved surface of each constituting the next adjacent portion to the other, as it the outer longitudinal half, or other than half, of each, as shownin the drawing, were removed and the leads 3 connected to the remaining or adjacent portions. in such modilied form, a consideration would be that no change should be permitted in the symmetry or localized degree of concentration of the field suilicient to cause the ultimate are to travel between other than substantially the nearest points on the portions 1. This result may be insured, as by rounding the farthermost edges of the members or by placing conducting shields adjacent thereto. Attend ing conditions, such as electric field distributions, and concentrations, temperature, humidity and wind velocity, of course affect the measurement, as with the usual sphere gaps.

The end portions 2, which may be omitted if the midportions 1 are sufiiciently long in consideration of the voltages to be used, are

. shoulders 4 fitted into the ends of the mid portion 1. The conducting lead and support 3 is also of suitable diameter to prevent concentration of the field thereon and is preferably connected to the mid portion 1 by a member 5 disposed therein as shown, or through mechanical support to the interior structural framework supporting the thin outer cylindrical conducting surface.

The cylindrical form of the mid portions 1 renders them very easy to manufacture of thin sheet metal or other suitable material and the end portions 2, since they are removed from the ultimate arcing surfaces of the members 1, need not be of the same size nor of'the same degree of accuracy as spheregap members for the same voltages. That is, they need not be of accurately turned and polished metal, but may be made'by a tinsmith' of thin sheet metal or other suitable material.

While I have shown and described a particular form of my invention, changes may be effected therein without departing from the 1 spirit and scope thereof, as set forth in the appended claims.

I claim as my invention '1. An arc-gap device comprising a pair of elongated term-inalmembers disposed in angular spaced relation and having adjacent conducting surfaces of substantially cylindrical curvature free-of field-disturbing portions within the zone of effective field operation between said members.

2. An arc-gap device comprising a pair of elongated terminal members disposed in angular spaced relation having adjacent conducting surfaces of substantially cylindrical curvature androunded ends to prevent field disturbance in the zone of effective field operation between said members. 7

3. An arc-gap device comprising a pair of elongated terminal members disposed in spaced substantially right-angular parallelplane relation and having adjacent conductlng surfaces ofv substantially cylindrical curvature free of field-disturbing portions within the zone of effective field operation be tween said members.

4. An arc-gap device comprising a pair of elongated terminal members disposed in August, 1925.

HAROLD B. SMITH. 

